Crews in Minneapolis were beginning on Sunday to repair the Martin Olav Sabo bike and pedestrian bridge, six months after a pair of cables supporting it broke loose.
Workers will retrofit one of the 18 diaphragm plates that secure the cables to the mast of the bridge spanning Hiawatha Avenue. The plates connect to cables, which help support the bridge.
In February, the topmost plate fractured, and an inspection found cracks in the one below it as well. Testing revealed the plates weren't strong enough to withstand vibrations caused by the wind.
The augmented plate will be 4.25 inches thick, more than five times as thick as the original.
Minneapolis Public Works Director Steve Kotke says the new plate design will address the problem with vibrations.
"Probably the simplest way for me to describe it is it's considerably thicker," Kotke says, "and that means it's going to be stiffer and it will be able to handle stresses better than the existing plate."
The city will test the plate for about a month. If the redesign works, the plan is to replace all 18 plates by the end of the year.
The cost of the investigation, engineering and repairs will approach $2 million. Minneapolis and Hennepin County are splitting the bill for now. They are talking with the firms that designed and built the five-year-old bridge about possible reimbursement.